UK Warns of Offshore Grating Failure

Fiber-reinforced plastic (FRP) deck gratings and other fire-resistant composite materials used in the offshore industry may fail, or lose integrity, after short exposure to hydrocarbon pool fires, UK health and safety regulators are warning.

The warning notice was issued Tuesday (Oct. 2) by Britain’s Health and Safety Executive (HSE), the counterpart to the U.S. Occupational Safety and Health Administration.

ASTM International

ASTM is developing a new specification for FRP gratings used in the marine environment. The draft document notes the material’s combustibility risk.

The notice, from the Hazardous Installations Directorate—Offshore Division, warns operators that the materials may fail more quickly than test protocols indicate.

HSE said the “fire-resistant composite materials, especially FRP deck gratings, used offshore may fail, or lose integrity, after exposure to relatively short duration hydrocarbon pool fires. The time taken for this is considerably shorter than the specified resistance period of 60 minutes derived from the certifying test for cellulosic fires.”

Operators “must determine whether composite gratings are used in areas with potential hydrocarbon fire exposure and identify means of ensuring the safety of personnel should they walk on weakened gratings," the warning said.

FRP Concerns

FRP deck gratings are commonly used by the offshore industry because they offer a lightweight alternative to steel gratings with improved environmental resistance and a fire-resistance certification, according to HSE.

FRP deck gratings are currently certified against U.S. Coast Guard specifications PFM 2-98 and NVIC 9-97-CH1, which employ a combination of load tests and a 60-minute fire exposure test. However, recent tests have determined that certain fire exposure might compromise the gratings' integrity.

Tests by the Health & Safety Laboratory (HSL), conducted on behalf of HSE, have determined that certain types of FRP gratings based on a glass reinforcement embedded in a phenolic or isophthalic resin may lose their load-bearing capabilities or fail after exposure to hydrocarbon pool fires.

Testing Findings

Testing for the U.S. Coast Guard specifications used a 60-minute cellulosic fire exposure, which has a slow growth time and may reach 880°C after 60 minutes, whereas a hydrocarbon fire can reach temperatures around 1100°C in significantly less time, HSE reported.

HSE

The Health and Safety Executive's Offshore Division warns that the materials may fail more quickly than previously believed.

The HSL tests determined that the fire duration required for failure or weakening is substantially shorter than for cellulosic fires against which the composite materials were certified. Testing also identified the possibility that the grating may appear to retain integrity post-fire, but may actually have insufficient strength to support people walking/running on it.

HSE is urging owners and operators to identify whether composites are used in areas where they may be exposed to hydrocarbon fires. If so, the operators must work with manufacturers and suppliers to ensure that “sufficient integrity will remain for their safe use.”

FRP Standard Underway

ASTM International announced last year that it was developing a new specification for FRP gratings used in marine construction and shipbuilding.

The draft specification notes that FRP gratings “are combustible and exhibit mechanical properties different than steel and thus require testing for structural integrity and surface flammability,” along with “careful consideration” of other factors related primarily to the harsh marine exposures.

This specification will address material requirements, construction, installation, and testing for molded and pultruded FRP gratings used in the marine environment.

Interesting. Sounds like they should update the required test protocol. Hydrocarbon pool fires certainly are more likely than cellulosic for the oil industry!

Comment from peter gibson, (10/5/2012, 11:35 AM)

Good example of not having the perfect coating/material. Strong in one area ;weak in another.

Comment from Larry Stephans, (10/9/2012, 9:52 AM)

Originally the testing of FRP grating for fire resistance was meant to insure that the grating was not a major source of fuel, i.e. would not significantly contribute to a fire. I am somewhat surprised that testing for structural integrity after exposure to a fire hasn't been done to sufficiently demonstrate without a doubt that the grating will support a load. I know I would be real reluctant to walk on FRP grating that has been exposed to fire for any length of time.